diff --git a/libuavcan/include/uavcan/protocol/file_server.hpp b/libuavcan/include/uavcan/protocol/file_server.hpp
index ef6008766c..ba458cefad 100644
--- a/libuavcan/include/uavcan/protocol/file_server.hpp
+++ b/libuavcan/include/uavcan/protocol/file_server.hpp
@@ -20,6 +20,8 @@ namespace uavcan
 {
 /**
  * The file server backend should implement this interface.
+ * Note that error codes returned by these methods are defined in uavcan.protocol.file.Error; these are
+ * not the same as libuavcan-internal error codes defined in uavcan.error.hpp.
  */
 class UAVCAN_EXPORT IFileServerBackend
 {